1. Field of the Invention
One embodiment of the present invention relates to a light-emitting element, a display device including the light-emitting element, an electronic device including the light-emitting element, or a lighting device including the light-emitting element.
Note that one embodiment of the present invention is not limited to the above technical field. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, and a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, a method for driving any of them, and a method for manufacturing any of them.
2. Description of the Related Art
In recent years, research and development have been extensively conducted on light-emitting elements utilizing electroluminescence (EL). In a basic structure of such a light-emitting element, a layer containing a light-emitting substance (an EL layer) is interposed between a pair of electrodes. By application of a voltage between the electrodes of this element, light emission from the light-emitting substance can be obtained.
Since the above light-emitting element is a self-luminous type, a display device using this light-emitting element has advantages such as high visibility, no necessity of a backlight, and low power consumption. Furthermore, such a light-emitting element also has advantages in that the element can be formed to be thin and lightweight, and that response time is high.
In the manufacturing process of a light-emitting element, an electrode serving as an anode of the light-emitting element is formed over a substrate before the other electrode serving as a cathode is formed as described above in some cases, and in other cases, an electrode serving as a cathode is formed over a substrate before the other electrode serving as an anode is formed. An element structure formed in the former cases of the manufacturing process is referred to as an “ordered stacked structure”, and an element structure formed in the latter cases is referred to as an “inverted stacked structure”. Not only these element structures of the light-emitting element are mutually inverted over a substrate, but also the element structures may differ from each other depending on the difference in manufacturing processes (e.g., Patent Document 1).
Furthermore, a structure in which an oxide semiconductor (OS) is used for a semiconductor layer of a field-effect transistor (FET) for controlling a light-emitting element has also been proposed. The FET including an oxide semiconductor is referred to as OS-FET. In particular, majority carriers in the OS-FET including In, Ga, and Zn as components of an oxide semiconductor are electrons, and the OS-FET is an n-channel FET. There is a report that the OS-FET is combined with a light-emitting element with an inverted stacked structure where a cathode is connected to the OS-FET, whereby the element characteristics can be improved (for example, Non-Patent Document 1).